package org.example;

import java.util.Arrays;

public class TestHeap {
    public int[] elem;
    public  int usedSize;


    public  TestHeap(){
        this.elem = new int[10];
    }

    public void initElem(int[] array){
        for (int i = 0; i < array.length; i++) {
            this.elem[i] = array[i];
            usedSize++;
        }
    }

    //创建堆
    public  void createHaep(){
        for (int parent = (this.usedSize-1-1)/2; parent >=0 ; parent--) {
            //向下调整:根结点每次往下调整
            siftDown(parent,this.usedSize);
        }
    }

    /**
     *
     * @param parent  每颗子树调整的时候  的 起始位置
     * @param usedSize  判断 每颗子树什么时候  调整 结束
     */
    private void siftDown(int parent, int usedSize) {
        int child = 2*parent+1;
        while (child<usedSize){ //child合法
            //找到左右孩子的最大值
            if( child+ 1 <usedSize  &&  elem[child] < elem[child+1]){
                child++;
            }
            if (elem[child]>elem[parent]){
                swap(elem,child,parent);
                parent = child;
                child = 2*parent +1;
            }else {
                break;
            }
        }
    }


    private void swap(int[] elem,int i,int j) {
        int tmp = elem[i];
        elem[i] = elem[j];
        elem[j] = tmp;
    }



    public  void offer(int val){
        if (isFull()){
            elem = Arrays.copyOf(elem,2*elem.length);
        }
        elem[usedSize] = val;
        siftUp(usedSize);
        usedSize++;

    }

    private void siftUp(int child) {
        int parent = (child-1)/2;
        while ( parent >=0 ){
            if(elem[parent]<elem[child]){
                swap(elem,child,parent);

                child = parent;
                parent = (child-1)/2;
            }else {
                break;
            }
        }

    }


    public boolean isFull(){
        return  usedSize == elem.length;
    }


    /**
     * 删除
     */
    public int poll(){
        if(isEmpty()) {
            return -1;
        }
        int val = elem[0];
        swap(elem,0,usedSize-1);
        siftDown(0,usedSize-1);
        usedSize--;
        return val;
    }

    public boolean isEmpty() {
        return usedSize == 0;
    }
    public int peek(){
        if(isEmpty()) {
            return -1;
        }
        return elem[0];
    }


    /**
     * 堆排序
     */
    //O(N) + o(n*logN) ->  o(n*logN)
    public void heapSort() {
        int end = usedSize-1;
        while (end > 0) {
            swap(elem,0,end);
            siftDown(0,end);
            end--;
        }
    }

}
